A force is a push or a pull that acts on an object due to the interaction with another object. Forces can cause changes in speed, direction, or shape of bodies.

True or False? Balanced forces produce a resultant force .

False. Unbalanced forces produce a resultant force.

What is a resultant force ?

A resultant force is a single force that represents the combined effect of all forces acting on an object. It determines both the direction and the magnitude of the overall force experienced by the object.

State the two possible outcomes when forces combine .

Forces can combine to produce either balanced or unbalanced forces.

Define balanced forces .

Balanced forces occur when the forces acting on an object are equal in magnitude and opposite in direction, resulting in no net force acting on the object.

When do unbalanced forces occur?

Unbalanced forces occur when the forces acting on an object are unequal in magnitude or not opposite in direction, resulting in a net force that causes the object to accelerate in the direction of the net force.

An object is travelling forward at a constant speed in a straight line. A force is applied perpendicular to the direction of the object's motion. What is the effect of the force on the object's motion?

If a force is applied perpendicularly to the direction of an object's motion, the object will change direction.

An object is travelling forward at a constant speed in a straight line. What is the effect on the object's motion if a forward acting force is applied?

If a forward acting force is applied to an object travelling at a constant speed in a straight line, the object will speed up (accelerate).

True or False? Newton's first law states that objects will continue to move at the same velocity even if a resultant force acts on them.

False. Newton's first law states that objects will continue to move at the same velocity when there is no resultant force acting on them.

What is the effect of a zero resultant force on an object's motion?

The effect of a zero resultant force on the motion of an object is that the object will: remain stationary if it is at rest continue to move with the same velocity if it is already moving

How is Newton's first law applied to objects with constant velocity?

Newton's first law states that objects with constant velocity will experience no change in their motion unless a resultant force is applied.

Define constant velocity .

Constant velocity refers to motion at a steady speed and in a straight line .

In what situation does an object experience no resultant force ?

The situation when an object experiences no resultant force when the forces acting on it are balanced , meaning the net force is zero.

What is the value of the frictional force on a car moving at a constant velocity with no resultant force acting on it?

The value of the frictional force is equal to the driving force , as both forces are balanced when the car moves at a constant velocity.

State Newton's first law of motion.

Newton's first law of motion states that: objects will remain at rest, or move with a constant velocity unless acted on by a resultant force .

When a non-zero resultant force is applied to an object, what are the two possible changes in the object's motion?

When a non-zero force acts on an object, the object can: change its speed change its direction

Define Newton's second law of motion .

The acceleration of an object is proportional to the resultant force acting on it, and inversely proportional to the object's mass.

For a given resultant force, an object with a greater mass will experience a ______ acceleration.

For a given resultant force, an object with a greater mass will experience a smaller acceleration.

True or False? Force and acceleration always act in the same direction.

True. The force and the acceleration produced both act in the same direction.

Three trolleys of different masses are each pushed with the same force. Which trolley has the smallest acceleration, and why?

The trolley with the largest mass , because acceleration is inversely proportional to mass for a given force.

Define Newton's third law of motion .

Whenever two bodies interact, the forces they exert on each other are equal in magnitude and opposite in direction .

What three conditions must be true for two forces to form a Newton's third law pair?

They must act on different objects ; be equal in size and opposite in direction ; and be the same type of force (e.g. both weight, or both normal contact force).

A book rests on a table. Its weight and the normal contact force from the table are equal and opposite. Is this a Newton's third law pair? Explain.

No. Both forces act on the same object (the book) and are different types of force (weight and normal contact force), so they are balanced forces, not a third law pair.

What is the true Newton's third law pair for the weight of a book resting on a table?

The gravitational pull of the Earth on the book (weight) and the gravitational pull of the book on the Earth (also weight) — equal, opposite, the same type of force, acting on two different objects.

When a person walks, the foot pushes backward on the ground and the ground pushes forward on the foot; these two forces are equal in ______ and opposite in direction.

When a person walks, the foot pushes backward on the ground and the ground pushes forward on the foot; these two forces are equal in magnitude and opposite in direction.

True or False? The push force of a foot on the ground and the push force of the ground on the foot act on the same object.

False. They act on two different objects — the foot and the ground.

Extension is the increase in length of a spring when a force is applied, found by subtracting the original length from the final length .

In the spring investigation, what are the independent and dependent variables?

Independent variable = force applied to the spring Dependent variable = extension of the spring

The masses are removed and the whole experiment is repeated three times so that an ______ length can be calculated

The masses are removed and the whole experiment is repeated three times so that an average length can be calculated.

On a force–extension graph, what does a straight line through the origin show?

It shows that the force is directly proportional to the extension , so the spring obeys Hooke's law.

True or False? Ruler measurements should be taken at eye level to avoid a parallax error.

True. Reading the ruler at eye level avoids a parallax error , which is a type of systematic error .

Why is a pointer attached to the bottom of the spring?

A pointer lets the extension be read from the ruler more precisely, reducing random error .

The extension of a spring is proportional to the applied force, up to the limit of proportionality.

Define spring constant .

The spring constant is the force per unit extension of a spring, measured in N/m ; it is a measure of how stiff the spring is.

Define the limit of proportionality .

The point beyond which the relationship between force and extension of a spring is no longer directly proportional .

If the force on a spring is doubled (within the limit of proportionality), the extension will ______ .

If the force on a spring is doubled (within the limit of proportionality), the extension will double .

True or False? Beyond the limit of proportionality, doubling the force on a spring will still double its extension.

False. Beyond the limit of proportionality, extension is no longer directly proportional to force.

Define circular motion .

Circular motion is the movement of an object along a circular path, where the object's velocity is constantly changing due to the change in direction.

True or False? In circular motion, an object's speed and velocity remain constant .

False. In circular motion, an object's speed may be constant, but its velocity is constantly changing due to the change in direction.

What happens to an object's velocity in circular motion ?

In circular motion, an object's velocity is always changing as it moves along the circular path.

How does a force cause an object to change direction in circular motion?

A force causes an object to change direction in circular motion when it acts at 90 degrees to the direction of travel.

What factors determine the force needed to maintain circular motion ?

The factors that determine the force needed to maintain circular motion depend on the mass of the object, the speed of the object, and the radius of the circular path.

True or False? A smaller radius of the circular path requires a smaller force to maintain circular motion at constant speed.

False. A smaller radius requires a greater force to maintain constant speed in circular motion.

True or False? Velocity is defined as the rate of change of displacement.

True. Velocity is defined as the rate of change of displacement.

What two factors are affected by the size of the radius of an object in circular motion?

The two factors that are affected by the size of the radius of an object in circular motion are how large the circular path is and the force required to maintain the motion.

True or False? A satellite orbiting a planet is an example of circular motion.

True. A satellite orbiting a planet is an example of circular motion.

True or False? The speed of an object in circular motion will increase if the force is increased providing that the mass and radius remain constant.

True. The speed of an object in circular motion will increase if the force is increased providing that the mass and radius remain constant.

True or False? The radius of an object in circular motion will increase if the force is increased providing that the mass and speed remain constant.

False. The radius of an object in circular motion will decrease if the force is increased providing that the mass and speed remain constant.

True or False? For an object in circular motion, an increased mass requires an increased force to keep the speed and radius constant.

True. For an object in circular motion, an increased mass requires an increased force to keep the speed and radius constant.

Friction is the force between two surfaces that impedes motion and produces heating.

True or False? Friction speeds up the motion of an object.

False. Friction opposes the motion of an object, slowing it down.

O LevelPhysicsCambridge (CIE)Flashcards1. Motion, Forces & Energy1.5 Forces

1.5 Forces (Cambridge (CIE) O Level Physics): Flashcards

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Cards in this collection (102)

Define force.
A force is a push or a pull that acts on an object due to the interaction with another object. Forces can cause changes in speed, direction, or shape of bodies.
True or False?
Balanced forces produce a resultant force.
False.
Unbalanced forces produce a resultant force.
What is a resultant force?
A resultant force is a single force that represents the combined effect of all forces acting on an object. It determines both the direction and the magnitude of the overall force experienced by the object.
State the two possible outcomes when forces combine.
Forces can combine to produce either balanced or unbalanced forces.
Define balanced forces.
Balanced forces occur when the forces acting on an object are equal in magnitude and opposite in direction, resulting in no net force acting on the object.
When do unbalanced forces occur?
Unbalanced forces occur when the forces acting on an object are unequal in magnitude or not opposite in direction, resulting in a net force that causes the object to accelerate in the direction of the net force.
An object is travelling forward at a constant speed in a straight line. A force is applied perpendicular to the direction of the object's motion. What is the effect of the force on the object's motion?
If a force is applied perpendicularly to the direction of an object's motion, the object will change direction.
An object is travelling forward at a constant speed in a straight line. What is the effect on the object's motion if a forward acting force is applied?
If a forward acting force is applied to an object travelling at a constant speed in a straight line, the object will speed up (accelerate).
True or False?
Newton's first law states that objects will continue to move at the same velocity even if a resultant force acts on them.
False.
Newton's first law states that objects will continue to move at the same velocity when there is no resultant force acting on them.
What is the effect of a zero resultant force on an object's motion?
The effect of a zero resultant force on the motion of an object is that the object will:
- remain stationary if it is at rest
- continue to move with the same velocity if it is already moving
How is Newton's first law applied to objects with constant velocity?
Newton's first law states that objects with constant velocity will experience no change in their motion unless a resultant force is applied.
Define constant velocity.
Constant velocity refers to motion at a steady speed and in a straight line.
In what situation does an object experience no resultant force?
The situation when an object experiences no resultant force when the forces acting on it are balanced, meaning the net force is zero.
What is the value of the frictional force on a car moving at a constant velocity with no resultant force acting on it?
The value of the frictional force is equal to the driving force, as both forces are balanced when the car moves at a constant velocity.
State Newton's first law of motion.
Newton's first law of motion states that: objects will remain at rest, or move with a constant velocity unless acted on by a resultant force.
When a non-zero resultant force is applied to an object, what are the two possible changes in the object's motion?
When a non-zero force acts on an object, the object can:
- change its speed
- change its direction
Define Newton's second law of motion.
The acceleration of an object is proportional to the resultant force acting on it, and inversely proportional to the object's mass.
What is the equation for Newton's second law?
$F = m a$
Where:
- $F$ = resultant force, measured in newtons (N)
- $m$ = mass, measured in kilograms (kg)
- $a$ = acceleration, measured in metres per second squared (m/s²)
A car of mass 900 kg accelerates at 9 m/s². Calculate the resultant force needed to produce this acceleration.
$F = m a = 900 \times 9 = 8100 N$
For a given resultant force, an object with a greater mass will experience a ______ acceleration.
For a given resultant force, an object with a greater mass will experience a smaller acceleration.
True or False?
Force and acceleration always act in the same direction.
True.
The force and the acceleration produced both act in the same direction.
Three trolleys of different masses are each pushed with the same force. Which trolley has the smallest acceleration, and why?
The trolley with the largest mass, because acceleration is inversely proportional to mass for a given force.
Define Newton's third law of motion.
Whenever two bodies interact, the forces they exert on each other are equal in magnitude and opposite in direction.
What three conditions must be true for two forces to form a Newton's third law pair?
They must act on different objects; be equal in size and opposite in direction; and be the same type of force (e.g. both weight, or both normal contact force).
A book rests on a table. Its weight and the normal contact force from the table are equal and opposite. Is this a Newton's third law pair? Explain.
No. Both forces act on the same object (the book) and are different types of force (weight and normal contact force), so they are balanced forces, not a third law pair.
What is the true Newton's third law pair for the weight of a book resting on a table?
The gravitational pull of the Earth on the book (weight) and the gravitational pull of the book on the Earth (also weight) — equal, opposite, the same type of force, acting on two different objects.
When a person walks, the foot pushes backward on the ground and the ground pushes forward on the foot; these two forces are equal in ______ and opposite in direction.
When a person walks, the foot pushes backward on the ground and the ground pushes forward on the foot; these two forces are equal in magnitude and opposite in direction.
True or False?
The push force of a foot on the ground and the push force of the ground on the foot act on the same object.
False.
They act on two different objects — the foot and the ground.
Define extension.
Extension is the increase in length of a spring when a force is applied, found by subtracting the original length from the final length.
In the spring investigation, what are the independent and dependent variables?
- Independent variable = force applied to the spring
- Dependent variable = extension of the spring
How is the force on the spring calculated from the hanging masses?
The force equals the weight of the masses, calculated using $W = m g$ with $g = 9.8 N/kg$ (multiply each mass in kg by 9.8).
The masses are removed and the whole experiment is repeated three times so that an ______ length can be calculated
The masses are removed and the whole experiment is repeated three times so that an average length can be calculated.
On a force–extension graph, what does a straight line through the origin show?
It shows that the force is directly proportional to the extension, so the spring obeys Hooke's law.
True or False?
Ruler measurements should be taken at eye level to avoid a parallax error.
True.
Reading the ruler at eye level avoids a parallax error, which is a type of systematic error.
Why is a pointer attached to the bottom of the spring?
A pointer lets the extension be read from the ruler more precisely, reducing random error.
Define Hooke's law.
The extension of a spring is proportional to the applied force, up to the limit of proportionality.
Define spring constant.
The spring constant is the force per unit extension of a spring, measured in N/m; it is a measure of how stiff the spring is.
Define the limit of proportionality.
The point beyond which the relationship between force and extension of a spring is no longer directly proportional.
What is the equation for Hooke's law?
The equation for Hooke's law is $F = k x$
Where:
- $F$ = force applied, measured in newtons (N)
- $k$ = spring constant, measured in newtons per metre (N m⁻¹)
- $x$ = extension of the spring, measured in metres (m)
A spring with spring constant 4900 N/m compresses from a length of 40 cm to 33 cm. Calculate the force applied.
Extension, x = 40 − 33 = 7 cm = 0.07 m
$F = k x = 4900 \times 0.07 = 343 N$
If the force on a spring is doubled (within the limit of proportionality), the extension will ______.
If the force on a spring is doubled (within the limit of proportionality), the extension will double.
True or False?
Beyond the limit of proportionality, doubling the force on a spring will still double its extension.
False.
Beyond the limit of proportionality, extension is no longer directly proportional to force.
Define circular motion.
Circular motion is the movement of an object along a circular path, where the object's velocity is constantly changing due to the change in direction.
True or False?
In circular motion, an object's speed and velocity remain constant.
False.
In circular motion, an object's speed may be constant, but its velocity is constantly changing due to the change in direction.
What happens to an object's velocity in circular motion?
In circular motion, an object's velocity is always changing as it moves along the circular path.
How does a force cause an object to change direction in circular motion?
A force causes an object to change direction in circular motion when it acts at 90 degrees to the direction of travel.
What factors determine the force needed to maintain circular motion?
The factors that determine the force needed to maintain circular motion depend on the mass of the object, the speed of the object, and the radius of the circular path.
True or False?
A smaller radius of the circular path requires a smaller force to maintain circular motion at constant speed.
False.
A smaller radius requires a greater force to maintain constant speed in circular motion.
True or False?
Velocity is defined as the rate of change of displacement.
True.
Velocity is defined as the rate of change of displacement.
What two factors are affected by the size of the radius of an object in circular motion?
The two factors that are affected by the size of the radius of an object in circular motion are how large the circular path is and the force required to maintain the motion.
True or False?
A satellite orbiting a planet is an example of circular motion.
True.
A satellite orbiting a planet is an example of circular motion.
True or False?
The speed of an object in circular motion will increase if the force is increased providing that the mass and radius remain constant.
True.
The speed of an object in circular motion will increase if the force is increased providing that the mass and radius remain constant.
True or False?
The radius of an object in circular motion will increase if the force is increased providing that the mass and speed remain constant.
False.
The radius of an object in circular motion will decrease if the force is increased providing that the mass and speed remain constant.
True or False?
For an object in circular motion, an increased mass requires an increased force to keep the speed and radius constant.
True.
For an object in circular motion, an increased mass requires an increased force to keep the speed and radius constant.
Define friction.
Friction is the force between two surfaces that impedes motion and produces heating.
True or False?
Friction speeds up the motion of an object.
False.
Friction opposes the motion of an object, slowing it down.
True or False?
Friction increases the temperature of an object.
True.
Friction causes heating, which raises the temperature of the object and its surroundings.
What creates friction between two solid objects?
Friction in solids is created by imperfections on the surfaces of the objects moving over one another.
Define fluids.
Fluids are substances that can flow and take the shape of their container. Gases and liquids are fluids.
Define drag.
Drag is the frictional force acting on objects moving through fluids, caused by collisions with the gas or liquid particles.
True or False?
Air resistance is a type of friction.
True.
Air resistance, experienced by objects moving through the air, is a type of friction that slows down their motion.
How does air resistance affect the temperature of an object?
Air resistance increases the temperature of an object by heating due to the work done against frictional forces as particles collide with the object.
True or False?
Drag is a type of friction.
True.
Drag is the frictional force acting on an object as the object moves through a fluid (a liquid or a gas).
Define stopping distance.
Stopping distance is the total distance travelled during the time it takes a car to stop in response to an emergency.
Define thinking distance.
Thinking distance is the distance travelled in the time it takes the driver to react to a hazard (their reaction time), measured in metres (m).
Define braking distance.
Braking distance is the distance travelled under the braking force after the brakes are applied, measured in metres (m).
Stopping distance = ______ distance + ______ distance.
Stopping distance = Thinking distance + Braking distance.
State the four factors that affect a vehicle's stopping distance.
Speed, mass, road conditions (e.g. wet or icy) and the driver's reaction time.
Why does a greater vehicle speed lead to a greater braking distance, for a given braking force?
At a higher speed, the brakes must do more work to bring the vehicle to a stop, so the braking distance increases.
True or False?
Being tired or under the influence of alcohol or drugs decreases a driver's thinking distance.
False.
Tiredness, alcohol and drugs increase a driver's reaction time, and therefore increase their thinking distance.
Define a moment.
A moment is the turning effect of a force about a pivot.
True or False?
Moments cause motion.
False.
Moments do not cause motion, they describe the turning effects due to forces about a pivot. The resultant force causes the motion.
What is the equation for calculating moments?
The equation used for calculating a moment is $M = F \times d$
Where:
- $M$ = moment, measured in newton metres (Nm)
- $F$ = force, measured in newtons (N)
- $d$ = perpendicular distance to the pivot, measured in metres (m)
What does the size of a moment depend upon?
The size of a moment depends on both the force applied and the perpendicular distance to the pivot.
True or False?
The equation for moments with respect to the perpendicular distance to the pivot is $d = \frac{F}{M}$
False.
The equation for moments with respect to the perpendicular distance to the pivot is $d = \frac{M}{F}$
State the units for the moment of a force.
The units for the moment of a force are newton metres (Nm).
True or False?
To reduce the force required to produce a moment, the distance from the pivot must be decreased.
False.
To reduce the force required to produce a moment, the distance from the pivot must be increased.
A force of 3 N is applied at a distance of 0.5 m from the pivot, what is the moment of the force?
When a force of 3 N is applied at a distance of 0.5 m from the pivot, the moment of the force is 1.5 Nm.
- $M = F d = 3 \times 0.5 = 1.5 Nm$
True or False?
The principle of moments applies to unbalanced systems.
False.
The principle of moments specifically applies to balanced systems.
True or False?
The principle of moments describes a system in equilibrium.
True.
The principle of moments describes the equilibrium condition in a balanced system.
True or False?
See-saws, beams and levers are systems that use the principle of moments.
True.
See-saws, beams and levers are systems that use the principle of moments.
Define equilibrium in terms of moments.
Equilibrium is a state in which an object remains unchanged in its motion or rotation, with balanced forces and moments acting upon it.
True or False?
In terms of moments, for an object to be in equilibrium it must be stationary.
False.
An object in equilibrium can either be stationary or moving with constant velocity.
What does it mean for the forces on an object to be balanced?
When the forces on an object are balanced, the net force acting on it is zero, resulting in no change in its motion.
What condition must be met for there to be no resultant force on an object?
The condition that must be met for there to be no resultant force on an object is that the forces acting on it must be balanced, cancelling each other out.
True or False?
In terms of moment, a system in equilibrium has a net force acting on it.
False.
A system in equilibrium has no net force acting on it, so the net force is zero.
What is the significance of balanced forces and moments in equilibrium on a system?
The significance of balanced forces and moments in equilibrium on a system is it remains unchanged in its state of motion or rotation, maintaining equilibrium.
Define the resultant moment.
The resultant moment is the net turning effect produced by the combination of all forces acting on an object, determining its rotational motion.
Define the centre of gravity.
The centre of gravity of an object is the point at which the weight of the object can be considered to act.
True or False?
The centre of gravity is always located at the geometric centre of an object.
False.
The centre of gravity can be located at the geometric centre of a regularly shaped object. This is not necessarily the case for irregularly shaped objects.
True or False?
The location of the centre of mass of an object affects its stability and balance.
True.
The location of the centre of mass of an object affects its stability and balance.
Define stability.
Stability refers to an object's ability to maintain its equilibrium position, where its centre of gravity lies above its base.
True or False?
An object is considered stable if its centre of gravity is below its base.
False.
An object is stable if its centre of gravity lies above its base, ensuring balance and preventing it from tipping over.
How does the width of the base affect an object's stability?
The width of an object's base affects its stability because a wider base makes it harder to tip over, increasing stability, while a narrower base makes it easier to tip over, decreasing stability.
What factors influence an object's stability?
An object's stability is influenced by the position of its centre of gravity and the width of its base.
State the condition required for an object to be stable.
An object is stable when its centre of gravity is positioned above its base, ensuring equilibrium and resistance to tipping.
How does the position of the centre of gravity affect stability?
The position of the centre of gravity determines whether an object will remain balanced or topple over when disturbed.
What happens to an object's centre of gravity when it is suspended from a point?
When an object is suspended from a point, it will settle so that its centre of gravity comes to rest below the pivoting point.
True or False?
In an experiment to find the centre of gravity of an irregular shape, a plumb line is used to draw a vertical line.
True.
The plumb line is used to draw a vertical line from the pivot to determine where the centre of gravity will lie.
How can you locate the centre of gravity of an irregular shape?
An irregular shape can be suspended from different points, and a plum line can be used to draw vertical lines that intersect at the centre of gravity.
What is the importance of determining the centre of gravity?
Determining the centre of gravity enables an understanding of the stability and balance of an object, which is crucial in various applications.
True or False?
The centre of gravity of an object is always fixed.
False.
The centre of gravity of an object may change depending on the object's orientation or composition, especially in flexible or complex structures.

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